Apparatus for and method of forming a tubular metal blank into a tapered tube on a tapered mandrel

ABSTRACT

A method of forming a tubular metal blank into a tapered tube on a tapered mandrel comprising disposing the tubular metal blank about the tapered mandrel, applying a bullet-shaped nose to an end of the mandrel and blank, pushing the tapered mandrel with the tubular metal blank thereabout with the bullet-shaped nose leading through an expandable die and by the bullet-shaped nose expanding the die to receive the leading end of the tubular metal blank and thereafter progressively collapsing the tubular metal blank about the tapered mandrel by continuing movement of the tapered mandrel with the tubular metal blank thereabout through the expandable die while exerting inward pressure on the tubular metal blank by the die to form a tapered tube on the tapered mandrel. Preferably the leading end of the tubular metal blank is interfitted with the bullet-shaped nose so that the bullet-shaped nose guides both the mandrel and blank through the die. After the bullet-shaped nose has passed through the die the mandrel and blank are pulled through the die. Preferably the bullet-shaped nose is removed and replaced by a fitting which is applied to the leading end of the mandrel and blank and the mandrel and blank are pulled through the die by pulling means cooperating with the fitting and the leading end of the mandrel and blank. Also apparatus for forming a tubular metal blank into a tapered tube on a tapered mandrel comprising an expandable die, a bulletshaped nose appliable to an end of the mandrel and blank, means for pushing through the expandable die the tapered mandrel with the tubular metal blank disposed thereabout and with the bulletshaped nose applied to the leading end of the mandrel and blank so that the bullet-shaped nose expands the die to receive the mandrel and blank and means for continuing the movement of the mandrel and blank through the die and exerting inward pressure on the blank by the die to collapse the blank about the mandrel. The end of the mandrel desirably has a reduced extension and the bullet-shaped nose may be applied over the reduced extension of the mandrel and may interfit with the end of the tubular metal blank. The means for continuing the movement of the mandrel and blank through the die are preferably pulling means pulling the mandrel and blank through the die by the leading end thereof. The bullet-shaped nose is preferably removable and a fitting is desirably provided which replaces the bullet-shaped nose after the bullet-shaped nose has passed through the die together with means cooperating with the fitting pulling the mandrel and blank through the die. The fitting may be applied over the end portion of the mandrel and snugly received in the leading end of the blank, and means including clamping jaws are preferably provided clamping the leading end of the blank against the fitting and pulling the mandrel and blank through the die. The mandrel may have a further reduced longitudinal projection projecting beyond the reduced extension and the fitting may be applied to such projection and locked against withdrawal therefrom.

United States Patent 1 Lesko [451 Jan. 30, 1973 M INTO A TAPERED TUBE ON A TAPERED MANDREL [75] inventor: Frank ,1. Lesko, Phoenix, Ariz.

[73] Assignee: Reynolds Metals Company,

Richmond, Va.

[22] Filed: Jan. 14,1971

[21] Appl. No.: 106,345

[52] US. Cl ..72l283, 72/284 [51] Int. Cl ..B21c H24 [58] Field of Search ..72/276, 283, 284

[56] References Cited UNITED STATES PATENTS 3,570,297 2/1972 Matthews ..72/276 2,597,500 5/1952 Kerr ..72/283 1,931,352 10/1933 Kemp ..72/274 3,327,513 6/1967 l-linshaw ..72/367 3,596,491 8/1971 Cress et a1. ..72/283 Primary ExaminerRichard J. Herbst Assistant Examiner-Michael]. Keenan Attorney-Glenn, Palmer, Lyne, Gibbs 8!. Thompson [57] ABSTRACT A method of forming a tubular metal blank into a tapered tube on a tapered mandrel comprising disposing the tubular metal blank about the tapered mandrel, applying a bullet-shaped nose to an end of the mandrel and blank, pushingthe tapered mandrel with the tubular metal blank thereabout with the bulletshaped nose leading through an expandable die and by the bullet-shaped nose expanding the die to receive the leading end of the tubular metal blank and thereafter progressively collapsing the tubular metal blank about the tapered mandrel by continuing movement of the tapered mandrel with the tubular metal blank thereabout through the expandable die while exerting inward pressure on the tubular metal blank by thedie to form a tapered tube on the tapered mandrel. Preferably the leading end of the tubular metal blank is interfitted with the bullet-shaped nose so that the bullet-shaped nose guides both the mandrel and blank through the die. After the bullet-shaped nose has passed through the die the mandrel and blank are pulled through the die. Preferably the bullet-shaped nose is removed and replaced by a fitting which is applied to the leading end of the mandrel and blank and the mandrel and blank are pulled through the die by pulling means cooperating with the fitting and the leading end of the mandrel and blank.

the tubular metal blank disposed thereabout and with the bullet-shaped nose applied to the leading end of the mandrel and blank so that the bullet-shaped nose expands the die to receive the mandrel and blank and means for continuing the movement of the mandrel and blank through the die and exerting inward pressure on the blank by the die to collapse the blank about the mandrel. The end of the mandrel desirably has a reduced extension and the bullet-shaped nose may be applied over the reduced extension of the mandrel and may interfit with the end of the tubular metal blank. The means for continuing the movement of the mandrel and blank through the die are preferably pulling means pulling the mandrel and blank through the die by the leading end thereof. The bullet-shaped nose is preferably removable and a fitting is desirably provided which replaces the bulletshaped nose after the bullet-shaped nose has passed through the die together with means cooperating with the fitting pulling the mandrel and blank through the die. The fitting may be applied over the end portion of the mandrel and snugly received in the leading end of the blank, and means including clamping jaws are preferably provided clamping the leading end of the 11 Claims,,6 Drawing Figures United States Patent 1 [111 3,713,318

PATENTEDJAN 30 ms SHEET 3 [IF 3 FIG.5.

INVENTOR.

FRANK J. LESKO ATTORNEYS APPARATUS FOR AND METHOD OF FORMING A TUBULAR METAL BLANK INTO A TAPERED TUBE ON A TAPERED MANDREL This invention relates to apparatus for and a method of forming a tubular metal blank into a tapered tube on a tapered mandrel. The tubular metal blank is initially of constant transverse dimension and is disposed about the tapered mandrel, and the tapered mandrel with the tubular metal blank thereabout is advanced through a die which collapses the tubular metal blank onto the tapered mandrel to form a tapered tube conforming to the taper of the mandrel. The die may be of various materials, the present preferred material being nonmetallic plastic material capable of being repeatedly stretched outwardly and contracted back to its original form, such, for example, as hard and tough nylon. The die may be mounted in a housing with means for applying fluid pressure in the housing against the outside of the die to collapse the tubular metal blank about the tapered mandrel as the tubular metal blank and mandrel pass through the die.

It has heretofore been proposed to reduce as by swaging the leading end of the mandrel to enable the mandrel to be pushed through the die to initiate the forming operation. I provide for eliminating the swaging operation by a novel provision which simplifies the operation and considerably reduces the labor cost. I apply what I call a bullet-shaped nose to an end of the tapered mandrel and tubular metal blank, push the mandrel with the tubular metal blank thereabout and with the bullet-shaped nose leading through the die and by the bullet-shaped nose expand the die to receive the leading end of the blank and thereafter progressively collapse the tubular metal blank about the tapered mandrel by continuing movement of the mandrel with the blank thereabout through the die while exerting inward pressure on the tubular metal blank by the die to form a tapered tube on the tapered mandrel. Preferably the leading end of the tubular metal blank is interfitted with the bullet-shaped nose so that the bullet-shaped nose guides both the mandrel and blank through the die. After the bullet-shaped nose has passed through the die the mandrel and blank are pulled through the die. Preferably the bullet-shaped nose is removed and replaced by a fitting which is applied to the leading end of the mandrel and blank and the mandrel and blank are pulled through the die by pulling means cooperating with the fitting and the leading end of the mandrel and blank.

Further, I provide apparatus for forming a tubular metal blank into a tapered tube on a tapered mandrel comprising an expandable die, a bullet-shaped nose appliable to an end of the mandrel and blank, means for pushing through the expandable die the tapered mandrel with the tubular metal blank disposed thereabout and with the bulletshaped nose applied to the leading end of the mandrel and blank so that the bullet-shaped nose expands the die to receive the mandrel and blank and means for continuing the movement of the mandrel and blank through the die and exerting inward pressure on the blank by the die to collapse the blank about the mandrel. The end of the ,mandrel desirably has a reduced extension and the bullet-shaped nose may be applied over the reduced extension of the mandrel and may interfit with the end of the tubular metal blank.

The means for continuing the movement of the mandrel and blank through the die are preferably pulling means pulling the mandrel and blank through the die by the leading end thereof. As indicated above the bullet-shaped nose is preferably removable, and l desirably provide a fitting which replaces the bullet-shaped nose after the bullet-shaped nose has passed through the die together with means cooperating with the fitting pulling the mandrel and blank through the die. The fitting may be applied over the end portion of the mandrel and snugly received in the leading end of the blank, and means including clamping jaws are preferably provided clamping the leading end of the blank against the fitting and pulling the mandrel and blank through the die. The mandrel may have a further reduced longitudinal projection projecting beyond the reduced extension and the fitting may be applied to such projection and locked against withdrawal therefrom.

Other details, objects and advantages of the invention will become apparent as the following description of a present preferred embodiment thereof and a present preferred method of practicing the same proceeds. E

In the accompanying drawings l have shown a present preferred embodiment of the invention and have illustrated a present preferred method of practicing the same in which FIG. 1 is a diagrammatic cross-sectional view with portions cut away of a tapered mandrel with a tubular metal blank disposed thereabout ready to be advanced through a nylon die to form the tubular metal blank into a tapered tube on the tapered mandrel showing a bullet-shaped nose applied to the mandrel and blank and a stripper mounted on the die housing;

FIG. 2 is a view similar to FIG. 1 showing themandrel and blank started through the die, showing the means for initially pushing the mandrel and blank through the die, loosening the tapered tube from the mandrel and withdrawing the mandrel from the tapered tube and showing the means for pulling the mandrel and blank through the die after the mandrel and blank have been started through the die;

P16. 3 is an isometric view showing the stripper mounted on the die housing; and

FIGS. 4, 5 and 6 are diagrams illustrating the operation of the stripper.

Referring now more particularly to the drawings, there is shown a mandrel designated as a whole by the letter M. The mandrel has a central uniformly tapered portion 2. At the larger end of the uniformly tapered portion 2 the mandrel has an end portion 3 of uniform transverse dimension and at the smaller end of the uniformly tapered portion 2 the mandrel has an end portion 4 of uniform transverse dimension. The mandrel may be hollow or solid transversely and may be sectional or unitary longitudinally. For simplicity of iilustration the mandrel is shown as a solid unitary steel mandrel with a threaded stud 5 at its larger end and a threaded stud 6 at its smaller end. The transverse or cross-sectional shape of the tapered portion 2 of the mandrel depends on the transverse shape of the tapered tube to be formed and the die presently to be described is correspondingly designed. For purposes of explanation and illustration the mandrel and die are shown as being of circular transverse shape.

The die is designated generally by the letter D. The form and design of the die and the material of which it is made constitute no part of the present invention so the die will not be described in detail. It is formed of hard and tough nylon and is capable of being repeatedly stretched outwardly and contracted back to its original form. In the form shown the die is of tapered U shaped cross section mounted in a housing 7 and pressed against the sides of the housing by a spreader cage 8. Fluid under pressure is admitted through a pipe 9 to the housing in the annular space surrounding and formed by the die and is discharged through a pipe 10. The pressure exerted by the fluid on the die is controlled by any suitable means such as a manually or automatically operated relief valve 11. As the mandrel and blank are advanced through the die the blank is progressively collapsed by the die about the tapered portion 2 of the mandrel to form a tapered tube.

The tubular metal blank to be formed into atapered tube on the mandrel is designated by the letter B. The inside diameter of the blank B is somewhat greater than the outside diameter of the larger cylindrical end portion 3 of the mandrel. For purposes of explanation and illustration the blank B may be deemed to be of aluminum or aluminum alloy. The tapered tube may be in a wide variety of sizes and used for the manufacture of such diverse products as baseball bats and lamp posts.

At the larger end of the mandrel is a flange 12. At the smaller end of the mandrel a nut 13 is threaded onto the stud 6; a sleeve 14 is welded to the nut 13. The sleeve 14 has bores 15 therethrough for a purpose to be presently described. The blank B is telescoped over the mandrel; the blank is introduced over the smaller end of the mandrel until it abuts the flange 12 as shown in FIG. 1. The opposite end of the blank terminates opposite the portion 4 of the mandrel as shown in FIG. 1, and the bullet-shaped nose 16 clearly shown in FIG. 1 is slipped over the end of the mandrel until it interfits with the end of the blank as shown. The bullet-shaped nose 16 has a bore 17 guidingly receiving the portion 4 of the mandrel and a kerf 18 receiving the end ofthe blank. The peripheral surface 19 of the bullet-shaped nose 16 is tapered. from a size at the front end smaller than the opening in the die when the die is in repose (i.e., not under pressure) to a size at the base of the kerf 18 the same as the outside diameter of the blank as clearly shown in FIG. 1. As is manifest from the above description and from FIG. 1 of the drawings, the bulletshaped nose 16 is free from fixed connection to the mandrel.

With the blank B and the bullet-shaped nose 16 thus assembled to the mandrel the mandrel is pushed to the right viewing FIG. 1 by means presently to be described. The blank B is pushed forward by the flange 12 of the mandrel and the blank B pushes forward the bullet-shaped nose 16 which is, maintained in proper alignment bythe portion 4 of the mandrel but is free at all times to be removed from the mandrel by being withdrawn to the right viewing FIG. 1. The bulletshaped nose passes through and progressively expands the die while the'die is still not under pressure until the leading end of the blank B has penetrated to the position shown in FIG. 2. The bullet-shaped nose 16 is removed and replaced by a fitting 20 having a bore'2l guidingly receiving the sleeve 14. A locking pin 22 is inserted through one of the bores 15 in the sleeve. The fitting 20 abuts the end of the portion 4 of the mandrel so the fitting is locked onto the mandrel by the pin 22. The fitting is sized to snugly fit into the end of the blank B and has its end tapered at 23 to facilitate entry into the blank. The mandrel is retracted to the left viewing FIG. 2 by means presently to be described. The blank is held against movement to the left with the mandrel by the die D. The fitting 20 enters the blank until the end of the blank engages the flange 24 of the fitting.

The apparatus includes the usual elongated bed (not shown) along which rides a carriage which may be of conventional construction and is equipped with means for clamping the work and pulling itthrough the die. The clamping means are designated generally by the numeral 25 and include clamping jaws 26. The carriage is moved in conventional manner to position for clamping the work and the clamping jaws 26 are operated to clamp the end of the blank B to the fitting 20 as shown in FIG. 2. Then the carriage carrying the clamping means is moved to the right along the bed, pulling the mandrel and blank through the die. Pressure is applied to the die which progressively collapses the blank onto the tapered mandrel as the mandrel and blank pass through the die forming a tapered tube.

Mounted on trunnions 27 is a cylinder 28 in which operates a piston 29. Portions of the piston extend out of both ends of the cylinder as shown in FIG. 2. The piston has a longitudinal passage 30 therethrough. Fluid under pressure may be admitted to and exhausted from the cylinder through either of two connections 31 and 32. The cylinder is in line with the mandrel M. An elongated member 33 which may be a length of cable extends through the longitudinal passage 30 in the piston and has a cable adapter 34 swaged thereto. The cable adapter 34 is threaded into a connecter 35 which in turn is threaded onto the stud 5. The opposite end of the cable 33 has a cable adapter 36 swaged thereto which in turn is threaded into a connector 37 which is connected with a flexible cable 38 which is wound on a reel 39 which may be hand operated or power driven. A spacer 40 is interposed between the left hand end of the piston viewing FIG. 2 and the connector 37.

The cable 38 is connected with the mandrel M through the cable 33. The tubular metal blank B is introduced over the mandrel M from right to left viewing FIGS. 1 and 2. To facilitate such introduction of the blank over the mandrel the right hand end of the mandrel is tilted upwardly, which tilting is accompanied by turning of the cylinder 28 through a small angle about the axis of the trunnions 27. The mandrel with the blank thereon and the cylinder are then returned to horizontal position and fluid under pressure is admitted to the cylinder through the connection 31. The piston moves to the right viewing FIG. 2; the right hand end of the piston engages the connector 35 and continued movement of the piston to the right-pushes the mandrel M and blank B with the bulletshaped nose 16 through the die D as above explained. As the mandrel advances it draws the cable 38 with it. When the blank reaches the position of FIG. 2 the bullet-shaped nose is replaced by the fitting 20, the clamping jaws 26 are applied and the mandrel and blank are pulled through the dieas above described. The stroke of the piston 29 need be only a fraction of the length of the mandrel since the piston pushes the mandrel only until the leading end of the blank passes through the die.

As the tapered tube is being formed by pulling of the mandrel and blank through the die the reel 39 continues paying out the cable 38. The length of the spacer 40 is such that just as the trailing end of the blank (now the tapered tube) passes through the die the connector 37 presses the spacer 40 against the left hand end of the piston, abruptly stopping the mandrel. The inertia due to the forward movement of the tapered tube loosens the tapered tube on the mandrel and facilitates withdrawal of the mandrel from the tapered tube.

Mounted on the right hand face of the housing 7 viewing FIGS. 1 and 2 are parallel L-shaped vertical guides 41 in which are slidably mounted upper and lower sections 42 and 43 respectively of a stripper designated as a whole by the letter S. The stripper sections are urged toward each other by tension coil springs 44. The lower edge of the stripper section 42 and the upper edge of the stripper section 43 have their opposed central portions cut out in semicircular form as shown in FIG. 3. The stripper sections are shown in fully closed or stripping position in FIG. 3 and in the diagrams FIGS. 4, 5 and 6.

The mandrel and tapered tube being formed pass through the circular opening in the stripper (FIG. 3.) As the larger end of the tapered tube being formed approaches the stripper the stripper sections ride up on the outer surface of the tapered tube being formed and separate somewhat against the action of the springs 44 and when the trailing larger end of the formed tapered tube passes through thestripper the stripper sections snap together behind the tapered tube. The stripper sections are designed so that when they are together the diameter of the circular opening formed between them is equal to the inside diameter of the larger end of the tapered tube; thus the end of the tube bears against the stripper through substantially the full area of the end surface of the tube.

FIG. 4 shows the tapered tubein process of formation with the mandrel and the formed portion of the tube passing through the stripper. FIG. 5 shows the stripper just having snapped into place behind the trailing larger end of the formed tapered tube. FIG. 6 shows the stripper holding the formed tapered tube against movement to the left as the mandrel is withdrawn, thus stripping the tube from the mandrel.

The mandrel is withdrawn by winding up the cable 38 on the reel 39. The piston 29 is moved to the left in the cylinder 28 by admitting fluid under pressure through the connection 32 and exhausting fluid through the connection 31. Thus upon withdrawal of the mandrel to the position of FIG. 1 the apparatus is ready for the next cycle of operation.

While I have shown and described a present preferred embodiment of the invention and have illustrated a present preferred method of practicing the same it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims.

I claim:

1. A method of forming a tubular metal blank into a tapered tube on a tapered mandrel comprising disposing the tubular metal blank about the tapered mandrel,

applying a bullet-shaped nose to an end of the blank, the bullet-shaped nose being free from fixed connection to the mandrel, pushing the tapered mandrel with the tubular metal blank thereabout with the bulletshaped nose leading through an expandable die and by the bullet-shaped nose expanding the die to receive the leading end of the tubular metal blank and thereafter progressively collapsing the tubular metal blank about the tapered mandrel by continuing movement of the tapered mandrel with the tubular metal blank thereabout through the expandable die while exerting inward pressure on the tubular metal blank by the die to form a tapered tube on the tapered mandrel.

2. A method as claimed in claim 1 including interfitting the leading end of the tubular metal blank and the bullet-shaped nose so that the bullet-shaped nose guides both the mandrel and the tubular metal blank through the die.

3. A method as claimed in claim 1 in which after the bullet-shaped nose has passed through the die the tapered mandrel with the tubular metal blank thereabout is pulled through the die. v

4. A method as claimed in claim 1 in which after the bullet-shaped nose has passed through the die the bullet-shaped nose is removed and the tapered mandrel with the tubular metal blank thereabout is pulled through the die.

5. A method as claimed in claim 1 in which after the bullet-shaped nose has passed through the die the bul let-shaped nose is replaced by a fitting which is applied to the leading end of the mandrel and blank and the mandrel and blank are pulled through the die by pulling means cooperating with the fitting and the leading end of the mandrel and blank.

6. Apparatus for forming a tubular metal blank into a tapered tube on a tapered mandrel comprising an expandable die, a bullet-shaped nose appliable to an end of the blank while being free from fixed connection to the mandrel, means for pushing through the expandable die the tapered mandrel with the tubular metal blank disposed thereabout and with the bullet-shaped nose applied to the leading end of the mandrel and blank so that the bullet'shaped nose expands the die to receive the mandrel and blank and means for continuing the movement of the mandrel and blank through the die and exerting inward pressure on the blank by the die to collapse the blank about the mandrel.

7. Apparatus as claimed in claim 6in which the end of the mandrel has a reduced extension and the bulletshaped nose isapplied over the reduced extension of the mandrel and interfits with the end of the tubular metal blank.

8. Apparatus as claimed in claim 6 in which the means for continuing the movement of the mandrel and blank through the die are pulling means pulling the mandrel and blank through the die by the leading end thereof.

9. Apparatus as claimed in claim 6 in which the bullet-shaped nose is removable and a fitting is provided which replaces the bullet-shaped nose after the bulletshaped nose has passed through the die together with means cooperating with the fitting pulling the mandrel and blank through the die.

10. Apparatus as claimed in claim 9 in which the fitting is applied over theend portion of the mandrel further reduced longitudinal projection projecting beyond the reduced extension and a fitting is applied to such projection and locked against withdrawal therefrom together with means cooperating with the fitting pulling themandrel and blank through the die. 

1. A method of forming a tubular metal blank into a tapered tube on a tapered mandrel comprising disposing the tubular metal blank about the tapered mandrel, applying a bullet-shaped nose to an end of the blank, the bullet-shaped nose being free from fixed connection to the mandrel, pushing the tapered mandrel with the tubular metal blank thereabout with the bullet-shaped nose leading through an expandable die and by the bullet-shaped nose expanding the die to receive the leading end of the tubular metal blank and thereafter progressively collapsing the tubular metal blank about the tapered mandrel by continuing movement of the tapered mandrel with the tubular metal blank thereabout through the expandable die while exerting inward pressure on the tubular metal blank by the die to form a tapered tube on the tapered mandrel.
 1. A method of forming a tubular metal blank into a tapered tube on a tapered mandrel comprising disposing the tubular metal blank about the tapered mandrel, applying a bullet-shaped nose to an end of the blank, the bullet-shaped nose being free from fixed connection to the mandrel, pushing the tapered mandrel with the tubular metal blank thereabout with the bullet-shaped nose leading through an expandable die and by the bullet-shaped nose expanding the die to receive the leading end of the tubular metal blank and thereafter progressively collapsing the tubular metal blank about the tapered mandrel by continuing movement of the tapered mandrel with the tubular metal blank thereabout through the expandable die while exerting inward pressure on the tubular metal blank by the die to form a tapered tube on the tapered mandrel.
 2. A method as claimed in claim 1 including interfitting the leading end of the tubular metal blank and the bullet-shaped nose so that the bullet-shaped nose guides both the mandrel and the tubular metal blank through the die.
 3. A method as claimed in claim 1 in which after the bullet-shaped nose has passed through the die the tapered mandrel with the tubular metal blank thereabout is pulled through the die.
 4. A method as claimed in claim 1 in which after the bullet-shaped nose has passed through the die the bullet-shaped nose is removed and the tapered mandrel with the tubular metal blank thereabout is pulled through the die.
 5. A method as claimed in claim 1 in which after the bullet-shaped nose has passed through the die the bullet-shaped nose is replaced by a fitting which is applied to the leading end of the mandrel and blank and the mandrel and blank are pulled through the die by pulling means cooperating with the fitting and the leading end of the mandrel and blank.
 6. Apparatus for forming a tubular metal blank into a tapered tube on a tapered mandrel comprising an expandable die, a bullet-shaped nose appliable to an end of the blank while being free from fixed connection to the mandrel, means for pushing through the expandable die the tapered mandrel with the tubular metal blank disposed thereabout and with the bullet-shaped nose applied to the leading end of the mandrel and blank so that the bullet-shaped nose expands the die to receive the mandrel and blank and means for continuing the movement of the mandrel and blank through the die and exerting inward pressure on the blank by the die to collapse the blank about the mandrel.
 7. Apparatus as claimed in claim 6 in which the end of the mandrel has a reduced extension and the bullet-shaped nose is applied over the reduced extension of the mandrel and interfits with the end of the tubular metal blank.
 8. Apparatus as claimed in claim 6 in which the means for continuing the movement of the mandrel and blank through the die are pulling means pulling the mandrel and blank through the die by the leading end thereof.
 9. Apparatus as claimed in claim 6 in which the bullet-shaped nose is removable and a fitting is provided which replaces the bullet-shaped nose after the bullet-shaped nose has passed through the die together with means cooperating with the fitting pulling the mandrel and blank through the die.
 10. Apparatus as claimed in claim 9 in which the fitting is applied over the end portion of the mandrel and is snugly received in the leading end of the blank together with means including clamping jaws clamping the leading end of the blank against the fitting and pulling the mandrel and blank through the die. 